There goes my plan!! So, I had to get myself and DS a FP+ for ToT even though only DH and DD will ride. As far as I understand, I couldn't split that FP+ for my party to ride two separate rides. I kept getting the message that I would be changing the FP+ entirely to a diff. attraction for the whole group.
After DH and DD ride ToT, the four of us WILL use the other two FP+ on ToyStory and Star Tours. So, after Star Tours, we won't be able to add a 4th because DS and myself didn't actually ride ToT even though the time window passed?!? so frustrating!